Will the X-Men join the Avengers?

For twenty years, this was the crossover that couldn’t happen. When Marvel Studios started building the MCU in 2008, it didn’t actually own its most famous mutants - the film rights to the X-Men belonged to 20th Century Fox, which spent two decades running its own separate X-Men saga a universe away. Iron Man and Wolverine could never share a frame. Captain America and Professor X lived in different cinematic realities, kept apart by a line in a contract. Fans dreamed about it and mostly assumed it would never legally happen.

Then, in 2019, Disney bought Fox - and the wall came down. Avengers: Doomsday is where the rubble finally clears. Patrick Stewart’s Xavier, Ian McKellen’s Magneto and a whole roster of classic-era mutants are confirmed (the full list). The impossible crossover is real. The only question left is how they share the screen.

Allies first, teammates maybe

Here’s the nuance most excited headlines skip: “the X-Men are in it” and “the X-Men join the Avengers” are not the same sentence.

These mutants aren’t MCU natives. The film doesn’t pretend they’ve secretly been here all along; instead it pulls them in from a separate, colliding reality - a dedicated mutant universe, complete with its own X-Mansion out in North Salem, New York. That framing is doing careful work. It lets Marvel honour the Fox films - these are recognisably those characters, played by those actors - while explaining, in-story, why the Avengers have never met them before. So the likeliest dynamic isn’t formal enlistment; it’s an emergency alliance. Two groups of heroes from two dying worlds, thrown into the same trench by a threat too big for either to face alone.

And Doom is precisely that threat. Xavier and Magneto have spent their entire lives arguing over how mutants and humans should coexist; the Avengers have their own baggage and their own turf. But an “existential threat” - a villain endangering not a city or a country but reality itself - has a way of ending those arguments fast. When the universe is actively ending, nobody checks jurisdiction. That’s the classic comic logic for putting rival teams shoulder to shoulder, and it’s exactly the pressure Doomsday applies.

The real prize is what comes after

So will they permanently become Avengers? Probably not here - and that’s by design. The lasting integration, mutants written into the MCU as a native, always-was part of the world, is a job for after Secret Wars, when reality gets rebuilt and Marvel can quietly rewrite history to include them. Doomsday is the introduction; the Mutant Saga that follows is the real payoff (the theory). Think of this film as the handshake, not the wedding.

There’s a bittersweet edge, too. Because these legacy X-Men are visitors from a collapsing reality, they’re also among the most expendable characters in the film - a story about dying universes has a built-in way to give them a heroic send-off. So savour the team-up; it may cost some of them.

And savour which mutants are back, because there’s real poignancy in it. Ian McKellen and Patrick Stewart first played Magneto and Professor X in 2000, in the film that arguably launched the modern superhero era - a full eight years before Iron Man. Channing Tatum is finally appearing as Gambit after his own solo movie collapsed in development for the better part of a decade. These aren’t just cameos; they’re careers coming full circle. Marvel isn’t only crossing two franchises - it’s handing a generation of X-Men actors the spotlight, and the send-off, that Fox never quite managed.

Keep one eye, too, on who else might wander in through that same multiversal door. With an entire mutant reality colliding into the MCU, the film has a built-in excuse to feature faces it hasn’t officially confirmed - which is exactly why speculation about a Wolverine or Deadpool cameo refuses to die. Whether or not those two show up, the principle holds: once you’ve established that mutants can cross over from a dying world, the roster of possible appearances becomes enormous, spanning every era of X-Men history. That’s the quiet genius of the “colliding realities” framing - it lets Marvel bring back almost anyone without having to explain how they fit. For a fanbase that spent twenty years watching these characters locked in a separate cinematic universe, Doomsday isn’t just a crossover. It’s a reunion, a victory lap and a door thrown wide open all at once.

Our call: likely - as an alliance, not a merger. Expect the X-Men and the Avengers to fight side by side against Doom in a moment two decades in the making, with the full, permanent team-up saved for the era the finale kicks off. After twenty years of “what if,” just seeing them in the same frame is the win.

← All predictions